The objective of the present invention is to provide a feeding arrangement enabling detection of the movement of a single phase stepping motor, as used for instance in a timepiece, and arranged to control the operation of the motor by supplying a first type of bipolar pulses of short duration or by supplying a second type of bipolar pulses of greater duration, pulse train of the second type being fed to the motor in the event that the motor has failed to step in response to a short duration pulse.
Arrangements of this type are already known. The German laid open specification DEOS 27 45 052 describes a control system which supplies the motor with a low energy signal if the motor load is low and a greater energy signal if the motor load is heavy and does so with the purpose of diminishing by approximately 60% the energy consumption of the timepiece. The device operates by transforming from the first type of signal to the second type of signal on determining the motor current curve form the peak of which is displaced towards the right when the motor load increases. Through detecting the position of the maxima it thus becomes possible to send to the motor a wide pulse, for instance 7.8 ms, whenever the mechanical moment increases, this being the case for example whenever the calendar date should be changed. Such a system is however incapable of detecting, following such wide pulse, whether or not the motor has advanced through a step. There may thus be circumstances here a series of pulses of greater width has been sent to the motor unnecessarily.
Another arrangement is described in French patent applications FR 2,384,289, FR 2,388,323 wherein the detecting of the motor step being foreseen. In these patent applications the motor arrangement is such as to provide a saturable zone. In these circumstances a detection pulse having on the order of one ms width enables detection of whether or not the rotor has turned. If the step has not been made a correction pulse (for instance 7.8 ms) is immediately sent to the motor and replaces the normal advancing pulse (3.9 ms). As already mentioned such a system requires a motor having a saturable zone and thus presents the difficulty of not always being applicable to every motor used within the industry. On the other hand it may be noted that the detection voltage is doubled whenever the motor makes its step. The present invention proposes a voltage difference much greater and this provides a greater security of operation as will be explained hereinafter.
Again there may be cited the Swiss published application CH 13 723/72 which proposes differentiation of the detection signal and prolongation of the advance pulse as a function of the mechanical load applied to the motor. This system presents the difficulty that the detection of the greatest rotor speed does not necessarily signify that the said rotor has stepped as will appear from the following explanations.
Finally U.S. Pat. No. 4,114,364 also proposes to prolong the advance pulse in response to the motor load. Aside from the fact that this system does not detect rotation of the rotor it further presents the difficulty of an increased energy consumption which is contrary to the present object.